Colonist trapped themselves while building walls.

[Rhombus]

I had a colonist attempt to fill in an area by building sandstone walls throughout a section between 2 mountains.  They built around themselves in a U shape such that they trapped themselves.  They could destroy their way out or mine if willing to but it wasted time and resources for them to do so. 
To replicate simply have them build a 4 x 4 or larger area of walls and watch them build. 

Very minor from my perspective but thought it worth mentioning. 

[Bquizma]

Its just the AI being idiots. Just be careful so your colonists don't starve to death that way.

[milon]

It would still be great if the game alerted us to this kind of situation. It's bad for the colonist, the colony, the CPU (the stuck pawn's AI keeps hammering the pathfinding algorithm), and for the player. Not Fun, in my opinion.

Not a bug, per se, but an opportunity for improvement.